Definition of Liver transplant

Liver transplant: Surgery to remove a diseased liver and replace it with a healthy liver (or part of one) from a donor. The most common reasons for liver transplantation in children is biliary atresia (a disease in which the ducts that carry bile out of the liver are missing or damaged) while in adults the most common reason for a liver transplant is cirrhosis (a disease in which healthy liver cells are killed and replaced with scar tissue).

There is no effective treatment for end-stage liver disease other than a transplant. The life of someone with kidney failure can be extended by dialysis and someone with a failing heart can sometimes be sustained by an implantable pump, but there is no machines that can take over the liver's functions. Until such machines can be devised, until an animal liver can replace a human one or until new livers can be grown from stem cells, there is total dependence on liver transplants.

Liver transplant may be from cadavers or living donors and involve the whole liver, a reduced liver or a liver segment. The donor livers in transplants were initially from cadavers. Donor livers from live donors are now in increasing use. Most transplants involve the whole organ. A reduced liver transplant may be done if the donor liver is too large for the recipient. In segmental transplants, a segment (often a lobe) of the liver is transferred from a living donor to a recipient. The first such recipients were children. Now some are adults. The liver segments in the donor and the recipient grow back to full size within about a month.

The donor must be an adult capable of giving informed consent. (The informed consent is not a simple bioethical matter because liver-lobe transplantation is not risk-free for the donor.)

To determine who is in the most critical need of a liver transplant, the United Network for Organ Sharing (UNOS) uses a system in the US that includes the Model for End-Stage Liver Disease (MELD) scoring system for adults and the Pediatric End-Stage Liver Disease (PELD) scoring system for children under 18 years of age. These scoring methods were set up so that donor livers could be distributed to those who need them most urgently, not just who had been on the waiting list the longest.

About 80 to 90% of recipients survive liver transplantation. Survival rates have improved over the past several years because of drugs like cyclosporine and tacrolimus that suppress the immune system and keep it from attacking and damaging the new liver.